Astronomer's guide to the solar system

A coloured satellite image of a sand dune on Mars, obtained by the High
Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars
Reconnaissance Orbiter (MRO) on August 24, 2009.

Dr Kukula explains: "A kilometre-wide patch of Martian desert shows sand dunes
criss-crossed with strange dark markings. Just like sand dunes on Earth
these features are shaped and sculpted by the wind. Sand slipping down the
steep slopes produces dark streaks on the sides of the dunes while
mini-tornadoes known as dust devils trace wandering paths across the
landscape, lifting the top layer of pale dust to reveal the darker sand
beneath."